XMM-Newton RGS First Light - HR1099 1

Image and text courtesy of ESA

RGS spectrum of HR1099

RGS spectrum of the star known as HR1099. The spectrum illustrates the way
the RGS works; it decomposes X-ray light into its components, like a prism
does with visible light. The inserted image shows what is referred to as a
banana image. The horizontal axis shows the detected X-ray photons (X-ray
light particles) plotted as a function of the position on the detector
(strip of nine CCDs) and as a function of the energy of the photons, as
determined by the CCDs, along the vertical axis. Get the
high resolution version.

Discovering the elements

The final two examples of the initial data collected by XMM-Newton take the
form of spectra. They are provided by one of the two Reflection Grating
Spectrometers (RGS). Just as in optical spectroscopy, different elements absorb
and emit light at specific and unique points of the radiation spectrum. The RGS
spread these out in the form of two "bananas", the two so-called "spectral
orders" of the instrument. Emission lines appear as distinct features in the
rainbow of X-ray colours, acting as signatures that reveal a great deal of
information to astronomers.

The RGS spectra of HR 1099 are examples. The graphs display peaks or lines
that correspond to the various elements present in the source. One can
distinguish for instance the presence of different types of iron, oxygen carbon
and neon. From the analysis of this data one can deduce the temperatures,
densities, abundances and velocities of the different materials.

"Firstly, the nice separation of the two spectral order bands shows the
resolution of the RGS CCDs is well up to expectations" comments Bert Brinkman,
RGS Principal Investigator. "For the spectrometers as a whole, the resolution
which is of prime importance, is exactly or marginally better than what we
expected after the ground calibrations. The instruments promise a lot for the
future."